Conventional steam turbines use a wheel and diaphragm or drum rotor construction with a traditional double shell casing. While single shell casings have also been used, such applications have been limited to wheel and diaphragm configurations, not drum rotor configurations. In addition, while individual nozzle ring assemblies have been used with IP sections of steam turbines, those IP sections typically have a traditional double shell casing to support the individual nozzle stages. Conventional steam turbines utilizing wheel and diaphragm construction are limited by the pressure limit of the single casing and the manufacture of the diaphragm being limited to a single stage.